• elderly;
  • survival;
  • Stage III colon cancer;
  • SEER

OBJECTIVES: To estimate the modifying effect of age on the survival benefit associated with adjuvant chemotherapy receipt in elderly patients with a diagnosis of Stage III colon cancer.

DESIGN: Observational, retrospective cohort study using two samples: an overall sample of 7,182 patients to provide externally valid analyses and a propensity score–matched sample of 3,016 patients to provide more internally valid analyses by reducing the presence of treatment endogeneity. An interval-censored survival model with a complementary log-log link was used. Hazard ratios and 95% confidence intervals were obtained for all regressions.

SETTINGS: Data from the National Cancer Institute's Surveillance, Epidemiology and End Results database and the linked Medicare enrollment and claims database were used.

PARTICIPANTS: Selected patients were aged 66 and older and had a diagnosis of Stage III colon cancer. Patients were followed from surgery to time of death or censorship.

MEASUREMENTS: The outcome was colon cancer–specific death during the follow-up period. Receipt of adjuvant chemotherapy was measured according to the presence of a claim for 5-fluorouracil or leucovorin within 6 months after surgery.

RESULTS: All elderly patients had a significant survival benefit associated with adjuvant chemotherapy receipt, although the survival benefit of adjuvant chemotherapy was not uniform across all age groups.

CONCLUSION: These findings have important clinical and policy implications for the risk–benefit calculation induced by treatment in older patients with Stage III colon cancer. The results suggest that there is a benefit from chemotherapy, but the benefit is lower with older age.